Numerical Simulation Studies Of BSF And Hetero-interface On A-Si:H(n)/c-Si(p) Heterojunction Solar Cell

It is of great scientific importance and practical value for investigation of a-Si: H/c-Si heterojunction solar cells on p-type crystalline silicon. Especially, because of the unique features of heterojunction, it can be effectively used to make high-performance silicon solar cells using mush little silicon materials and with higher stability. Therefore, it has important applications in the field of photovoltaics. In this paper, properties of back face field and hetero-interface are investigated numerically using computer simulation tools, and some innovative research results have been obtained.Firstly, based on energy band theory and recombination theory and charge carrier transmission theory and the interactional theory between solar light and semiconductor, the formation condition of effective back surface filed and the action mechanism of back surface filed on solar cell basic parameters are investigated numerically. When back surface filed has good conductivity, the fill factor can be improved. Furthermore, it can be found out that the short-circuit current can be improved by the enhanced spectra response in the short wavelength light absorbed by back surface filed and the open-circuit voltage can be influnced by the activation energy of back surface filed and the conduction band offset and the valence band offset between back surface and substrate. The phenomenon exhibits particular application for selecting appropriate back surface filed metarials.Secondly, based on the quasi- c-Si model, the action mechanism of the hetero-interface defect states on the substrate resistivity and the hetero-interface defect states on the solar cell basic parameters are investigated numerically. When the substrate resistivity is big, surface recombination in the hetero-interface defect states can not be affected. But this will change when the the substrate resistivity is very small and surface recombination in the hetero-interface defect states will be enhanced greatly. On the other hand, the absorbed spectra structure and the optical properties can be changed by the shrunken space charge room of the c-Si side and the expansile space charge room of the a-Si: H side during the decreasing of the substrate resistivity. It can be found out that there are different action mechanism between the front hetero-interface defect states and the rear hetero-interface defect states. The front hetero-interface defect states mainly make the open-circuit voltage decaying while the latter are mainly responsible for the decay of the short-circuit current. Fourthermore, it can be also found out that, when the substrate resistivity is very small, enhanced surface recombination in the shrunken space charge room of the front c-Si side and the rear c-Si side can effectively reduce the the open-circuit voltage and the short-circuit current respectively. The phenomenon exhibits particular application for selecting appropriate substate resistivity and hetero-interface defect states density.